Arrowhead Research Advances ARC-520 into IND-Enabling Studies for the
Treatment of Hepatitis B and Provides Guidance on Development Timeline

June 06, 2012 07:00 AM Eastern Daylight Time

PASADENA, Calif.--(BUSINESS WIRE)--Arrowhead Research Corporation (NASDAQ: ARWR), a targeted therapeutics
company, today announced that its hepatitis B virus (HBV) program has
completed all internal preclinical requirements and has named a clinical
candidate. As such, the Company has initiated the final IND-enabling
steps, including GMP manufacturing, GLP toxicology, and preparation of a
pre-IND data package for the US FDA and foreign counterparts. The
candidate, named ARC-520, is an RNAi therapeutic actively targeted to
the liver using the company’s Dynamic Polyconjugate (DPC) delivery
system and includes two siRNA sequences targeting two different regions
of the HBV genome.

“Chronic HBV infection is a serious global health problem with no cure,
and we believe ARC-520 can potentially have a substantial impact on
patient care worldwide,” said Dr. Bruce Given, Arrowhead’s Chief
Operating Officer and head of R&D. “We will continue to take an
aggressive stance on development timelines for ARC-520. We anticipate
filing an IND in Q2 of 2013 and our plan is to conduct a phase 1
clinical trial in chronic HBV carriers to provide early proof of
concept.”

The RNA sequences used in the clinical candidate were part of a
large-scale screening program initiated by Roche prior to the
acquisition by Arrowhead. The RNAs target regions highly conserved
across the major HBV genotypes and ARC-520 contains two distinct RNAs as
a strategy to minimize the potential development of resistance in
individual patients. Consistent with the company’s overarching strategy,
the DPCs used in ARC-520 employ active ligand-mediated targeting
specific to a receptor on hepatocytes. This approach results in
high-potency knockdown of a target gene, validated in mice, rats, and
non-human primates and it has demonstrated a low toxicity profile in
primates enabling long term dosing.

“The promotion of ARC-520 as a clinical candidate, so soon after
acquiring the Roche RNAi assets, represents an important milestone for
Arrowhead,” said Dr. Chris Anzalone, President and Chief Executive
Officer of Arrowhead. “This program follows in the footsteps of our
clinical stage targeted delivery programs in obesity with Adipotide® and
in cancer with RONDELTM and further validates our commitment
to ligand-mediated delivery in fields where most delivery is untargeted.
We believe that targeting holds great promise in allowing delivery of
currently undeliverable agents, such as many RNAs, and may also
dramatically improve the balance of safety and effectiveness for many
types of small molecule drugs.”

Highlights from the preclinical development program for ARC-520 have
been presented at recent scientific conferences and publication of
additional data is anticipated over the coming months in peer-reviewed
scientific journals.

About Arrowhead Research Corporation

Arrowhead Research Corporation is a clinical stage targeted therapeutics
company with development programs in oncology, obesity, and infectious
disease. The company leverages its platform technologies to design and
develop peptide-drug conjugates (PDCs) which specifically home to cell
types of interest while sparing off-target tissues, targeted drugs based
on the gene silencing RNA interference (RNAi) mechanism, and works with
partners to create improved versions of traditional small molecule drugs.

This news release contains forward-looking statements within the
meaning of the "safe harbor" provisions of the Private Securities
Litigation Reform Act of 1995. These statements are based upon our
current expectations and speak only as of the date hereof. Our actual
results may differ materially and adversely from those expressed in any
forward-looking statements as a result of various factors and
uncertainties, including our ability to finance our operations, the
future success of our scientific studies, our ability to successfully
develop drug candidates, the timing for starting and completing clinical
trials, rapid technological change in our markets, and the enforcement
of our intellectual property rights. Arrowhead Research Corporation's
most recent Annual Report on Form 10-K and subsequent Quarterly Reports
on Form 10-Q discuss some of the important risk factors that may affect
our business, results of operations and financial condition. We assume
no obligation to update or revise forward-looking statements to reflect
new events or circumstances.